In the manufacture of blood dialysis cartridges or similar mass transfer equipment, it is necessary to remove from the semipermeable hollow fibers which carry the blood to be dialyzed, the organic oils introduced into the fibers during their manufacture as a perservative. Normallly, this is done by soaking the fibers or flushing them with an appropriate solvent at a convenient step in the cartridge assembly process. For reasons related to the nature of the material and to the dimensional parameters involved, eight to ten washes are normally required to bring the oil content of fibers down to clinically acceptable levels. This procedure is quite time-consuming and expensive. In addition, it is wasteful of solvent and, with certain solvents, tends to attack the glycerin in the fiber walls which give the fibers their essential permeability characteristics.
It has also been found that when fiber ends, in the course of manufacturing a cartridge, are potted in polyurethane to form a manifold, sealing problems between the polyurethane and the fiber walls arise more because of the moisture content of the highly hygroscopic cellulose fibers than because of oil residues on the fiber walls. Due to the heat sensitivity of the fibers used in blood dialyzers, process temperatures of 50.degree. C. or above are not allowed. This rules out conventional oven-drying methods.